1. Field of the Invention
The present invention relates generally to bioremediation and to an improved method and apparatus for bacterial cultivation, preferably for growth of substrate specific micro-organisms that are then used in industrial wastewater remediation. More particularly, the present invention relates to an improved method and apparatus for cultivating strains of bacteria in various medium (e.g. nutrients and water), under aerobic conditions and thereafter discharging the combination of concentrated bacteria and medium downstream to a reservoir that contains wastewater to be treated. The aeration and circulation of fluids is designed to limit cells shearing and damage yet achieve critical cell mass (between about 1×107 and 1×1012 cfu (colony forming units) per milliliter and dissolved oxygen levels during cultivation. Critical cell mass is the minimum number of bacterial cells per milliliter required to achieve effective bioremediation.
2. General Background of the Invention
The remediation of industrial wastewater has in the past employed various bacteria. One application where this desired remediation is particularly useful is in the pulp and paper industry. The pulp and paper industry in the United States is one of the largest fully integrated industries in the world. Each year, mills in every part of the country produce millions of tons of paper and paper products for domestic and foreign use. The Environmental Protection Agency estimates the total value of shipments from the pulp and paper industry as close to $135 billion, as much as the petroleum refining industry.
Pulp and paper manufacturing involves a series of steps, each producing one or more characteristic wastes. A typical pulp and paper mill discharges from 25,000 to over 100,000 liters of wastewater for each air-dried ton of pulp produced. While the wastewater is discharged into the environment only after it has received on-site treatment, it still contains contaminant substances and residual organic solids. Mills discharging liquid waste into rivers and coastal waters are required, pursuant to the Waste Management Act, to obtain site-specific effluent discharge permits. Because of the potential for fines and the possibility of temporary or permanent closure, maintenance of the wastewater treatment is of great importance to owners and operators within the industry. The following tables summarize the typical processes and associated contaminants with paper manufacturing.
TABLE 1Typical Paper Industry Operations: Materials Used and Hazardous Wastes that Might be GeneratedProcess/General Types ofOperationMaterials UsedWaste GeneratedChemicalAcids/alkalies, lime,Acid/alkaline wastePulpingsulfurous acid, sodiumhydroxide, sodiumsulfideBleachingChlorine bleaches,Toxic wastewatersulfate bleaches,and wastewaterchloroform, solventstreatment sludge,Acid/alkaline wastePapermakingPigmentsWastewatertreatment sludgeSizing andWaxes, glues, syntheticToxic waste,Starchingresins, hydrocarbonsincludingwastewaters andsludgesCoating,Inks, paints, solventsSolvent waste, inkColoring, andrubbers, dyeswaste, paint waste,Dyeingignitable waste,toxic wasteCleaning andTetrachloroethylene,Solvent waste,DegreasingTrichloroethylene,toxic rinse watermethylene chloride,trichloroethane, carbontetrachloride
TABLE 2Paper Industry Waste DescriptionsWaste TypeDesignations/Trade NamesSpent SolventsOther Toxic or Ignitable WastesCarbonCarbon Tetrachloride, Carbon Tet,TetrachlorideTetrachloromethaneMethylene ChlorideMethylene Chloride, DichloromethaneTetrachloroethyleneTetrachloroethylene, Perchloroethylene,PCE1,1,1-1,1,1-Trichloroethane, 1,1,1-TCATrichloroethaneTrichloroethyleneTrichloroethylene, TCEChloroformChloroformBenzeneEthylene DichlorideEthylene Dichloride, 1,2-DichloroethaneChlorobenzeneChlorobenzene, Monmhlombenzene, PhenylChlorideMethyl EthylMethyl Ethyl Ketone, Methyl Acetone,Ketone-Meetco, But@one, Ethyl Methyl Ketone,MEK, 2-BenzeneMixed SpentHalogenated SolventsPetroleumPetroleum DistillatesDistillatesWaste TypeHazard ClanUN/NAID NumberWaste CarbonORM-AUN1846TetrachlorideWasteORM-AUN1593DichloromethaneWasteORM-AUN1897TetrachloroethyleneWaste 1,1,1-ORM-AUN2831TrichloroethaneWasteORM-AUN1710TrichloroethyleneWaste ChloroformORM-AUN1888Waste BenzeneFlammableUN1114(Benzol)Liquid 2Waste EthyleneFlammableUN1184DichlorideLiquidWaste ChlorobenzeneFlammableUN1134LiquidWaste Methyl EthylFlammableUN1193KetoneLiquidHazardous Waste:ORM-ENA9199Liquid, NOSWaste PetroleumFlammableUN1268DistillateLiquidCombustibleUN1268Liquid 4DesignationsTrade NamesCorrosive WastesAmmonium HydroxideAmmonium Hydroxide, Aqueous Ammonia,Ammonia Water, Spirit of HartshomHydrobromic AcidHydrobromic AcidHydrochloric AcidHydrochlonc Acid, Muriatic AcidHydrofluoric AcidHydrofluoric AcidNitric AcidNitric Acid, AquafortisPhosphoric AcidPhosphoric Acid, Orthophosphoric AcidPotassium HydroxidePotassium Hydroxide, Caustic PotashSodium HydroxideSodium HydroxideSulfuric AcidSulfuric Acid, Oil of VitriolOther Wastes andGeneral ClassificationsPaint Waste withCorrosive Liquid; Corrosive Solid;Heavy metalsIgnitable Wastes, NOS; Hazardous Wastes,NOSPaint Waste withCorrosive Liquids; Corrosive Solids;Heavy MetalsIgnitable Wastes, NOS
Within the industry, bacteria and their enzymes, along with some fungi and critical nutrient additives, have proven to be effective agents for in-situ remediation of organic wastes and subsurface pollution in soils, sediments and wastewaters associated with these processes. Effective management of a microbiological population can provide both short-term or long-term effluent improvements meeting tightening environmental restrictions, while minimizing capital expenses.
Environmental professionals are expected to “do more with less” by squeezing every ounce of performance out of the wastewater treatment system. In some cases, the quality or quantity of influent to the system has changed so much that the treatment system's design is no longer adequate to achieve the desired results. In other cases, the treatment system's capabilities have deteriorated while effluent requirements have become more stringent. In either case, innovative approaches may be necessary to allow the mill to simultaneously meet its environmental requirements, while also realizing its financial goals. Traditional waste treatment control strategies have focused on monitoring and controlling system parameters. Bioaugmentation involves applying biological additives to enhance the performance of secondary or biological wastewater treatment systems, focusing on managing the bacterial population (i.e. the work force) of the system.
In order to optimize the performance of the microbiological population, a comprehensive approach must be used to manage the system. Understanding how mill upsets and operational problems affect the microbiological population is critical to optimizing the wastewater treatment plant. Bioaugmentation has been practiced since the early 1960s. Given a history that includes misapplication of additives and poor documentation of results, the technology has come to be regarded as less than scientific in some circles. In many cases, rather than actively managing the treatment system through bioaugmentation, mills have adopted the widespread belief that over time, the proper microbes will populate the system and become acclimated to its influent. This belief assumes that the indigenous population, which is introduced via routes such as windblown solids, rainwater, and the plant influent stream, will always contain the organisms that are best suited for the service. In reality, even though the natural population may develop into an acceptable one, there may be performance limitations that only can be overcome by the introduction of additional microorganisms.